Improve qualcomm end-to-end user experience

[abhinaykukkadapu]

This is a task to capture all the things we need to improve in Qualcomm user flow:

1. Improve AOT experience
2. Improve build from source
3. Improve building binaries workflow

Current top pain points:

1. Fragmented entry points and user experience downloading QNN sdk and Android NDK, libc++ - unify the download paths, be transparent instead of silently downloading 2+GB sdks
2. Retry downloads on failures
3. Start from partial downloads on retry
4. Cache downloaded sdks
5. Build QNN on linux by default (enable via pybind.cmake) - enable download QNN_SDK during cmake
6. In build from source path, enable QNN by default on linux
7. Make glibc search and fallback transparent
8. Manage all QNN sdk version config at a single point instead of hardcoded paths
9. Set all env vars after downloading the sdk